North Korea's latest missile launch is its 20th in 2017 — and it seems to dash the idea that Pyongyang's lull in weapons testing over the past two months indicated a willingness to negotiate.

There had been 74 days between Tuesday's test and the last North Korean provocation, a missile launch on Sept. 15 that capped off a bout of activity over the summer months. Some hoped that this apparent lull might show that Washington's hard-line policy on North Korea was working or that Pyongyang was open to a “freeze for freeze” policy like that advocated by China and Russia.

Instead, just before 3 a.m. local time, North Korea fired a missile to the east. The Japanese Defense Ministry said the missile appeared to have flown for about 50 minutes. This missile test may prove a theory put forward by analysts such as Shea Cotton, a research associate at the James Martin Center for Nonproliferation Studies: The lack of weapons tests from North Korea was not strategic — it was seasonal.

Data compiled by Cotton shows that since Kim Jong Un took power in North Korea in late 2011, there has been a dramatic surge in the number of missile tests. However, these missile tests tended to take place only in the first three quarters of the year. Of the 76 missile tests conducted since 2012, only six have ever taken place in October, November or December.

The slowdown in testing in the last quarter of each year seems to be due to seasonal changes. Fall is harvest time in North Korea, and the country often needs its military to help out. The Korean People's Army also enters its training cycle in winter, taking further energy away from the weapons program.

But it is far from unheard of for North Korea to test weapons in the last three months of the year. In both 2015 and 2016, North Korea tested two missiles in the fourth quarter. And gaps of two months between tests are not unusual either: After the last missile test of 2016 on Oct. 19, it took 116 days for North Korea to resume testing.

For world powers, this is far from reassuring. Despite considerable international tension, as well as diplomatic and economic pressure — even the threat of an outright nuclear war which would devastate the country — North Korea has persisted with its missile program at a grimly predictable pace.

And worse, it's made considerable technological advances: Early estimates from David Wright, a senior scientist for the Union of Concerned Scientists, suggest that Tuesday's missile test showed “more than enough range to reach Washington, D.C., and in fact any part of the continental United States.”